diff --git a/lib/utils/entity-text.js b/lib/utils/entity-text.js
--- a/lib/utils/entity-text.js
+++ b/lib/utils/entity-text.js
@@ -31,7 +31,9 @@
       +name?: ?string,
       // displays threadInfo.name if set, or 'user1, user2, and user3'
       +display: 'uiName',
-      +uiName: string,
+      // If uiName is EntityText, then at render time ThreadEntity will be
+      // replaced with a pluralized list of uiName's UserEntities
+      +uiName: $ReadOnlyArray<UserEntity> | string,
     }
   | {
       +type: 'thread',
@@ -212,11 +214,25 @@
 function getNameForThreadEntity(
   entity: ThreadEntity,
   threadID: ?string,
-  params?: EntityTextToRawStringParams,
+  params?: ?EntityTextToRawStringParams,
 ): string {
   const { name: userGeneratedName, display } = entity;
   if (entity.display === 'uiName') {
-    return userGeneratedName ? userGeneratedName : entity.uiName;
+    if (userGeneratedName) {
+      return userGeneratedName;
+    }
+    const { uiName } = entity;
+    if (typeof uiName === 'string') {
+      return uiName;
+    }
+    let userEntities = uiName;
+    if (!params?.ignoreViewer) {
+      userEntities = userEntities.filter(innerEntity => !innerEntity.isViewer);
+    }
+    const pluralized = pluralizeEntityText(
+      userEntities.map(innerEntity => [innerEntity]),
+    );
+    return entityTextToRawString(pluralized, params);
   }
   invariant(
     entity.display === 'shortName',
@@ -261,7 +277,7 @@
 };
 function entityTextToRawString(
   entityText: EntityText,
-  params?: EntityTextToRawStringParams,
+  params?: ?EntityTextToRawStringParams,
 ): string {
   const textParts = entityText.map(entity => {
     if (typeof entity === 'string') {
@@ -343,22 +359,104 @@
 }
 
 type TextEntity = { +type: 'text', +text: string };
+type ShadowUserEntity = {
+  +type: 'shadowUser',
+  +username: string,
+  +originalUsername: string,
+};
 type EntityTextComponentAsObject =
   | UserEntity
   | ThreadEntity
   | ColorEntity
-  | TextEntity;
+  | TextEntity
+  | ShadowUserEntity;
 function entityTextToObjects(
   entityText: EntityText,
 ): EntityTextComponentAsObject[] {
-  return entityText.map(entity =>
-    typeof entity === 'string' ? { type: 'text', text: entity } : entity,
-  );
+  const objs = [];
+  for (const entity of entityText) {
+    if (typeof entity === 'string') {
+      objs.push({ type: 'text', text: entity });
+      continue;
+    }
+    objs.push(entity);
+    if (
+      entity.type === 'thread' &&
+      entity.display === 'uiName' &&
+      typeof entity.uiName !== 'string'
+    ) {
+      for (const innerEntity of entity.uiName) {
+        if (typeof innerEntity === 'string' || innerEntity.type !== 'user') {
+          continue;
+        }
+        const { username } = innerEntity;
+        if (username) {
+          objs.push({
+            type: 'shadowUser',
+            originalUsername: username,
+            username,
+          });
+        }
+      }
+    }
+  }
+  return objs;
 }
 function entityTextFromObjects(
   objects: $ReadOnlyArray<EntityTextComponentAsObject>,
 ): EntityText {
-  return objects.map(entity => (entity.type === 'text' ? entity.text : entity));
+  const shadowUserMap = new Map<string, string>();
+  for (const obj of objects) {
+    if (obj.type === 'shadowUser' && obj.username !== obj.originalUsername) {
+      shadowUserMap.set(obj.originalUsername, obj.username);
+    }
+  }
+  return objects
+    .map(entity => {
+      if (entity.type === 'text') {
+        return entity.text;
+      } else if (entity.type === 'shadowUser') {
+        return null;
+      } else if (
+        entity.type === 'thread' &&
+        entity.display === 'uiName' &&
+        typeof entity.uiName !== 'string'
+      ) {
+        const uiName = [];
+        let changeOccurred = false;
+        for (const innerEntity of entity.uiName) {
+          if (typeof innerEntity === 'string' || innerEntity.type !== 'user') {
+            uiName.push(innerEntity);
+            continue;
+          }
+          const { username } = innerEntity;
+          if (!username) {
+            uiName.push(innerEntity);
+            continue;
+          }
+          const ensName = shadowUserMap.get(username);
+          if (!ensName) {
+            uiName.push(innerEntity);
+            continue;
+          }
+          changeOccurred = true;
+          uiName.push({
+            ...innerEntity,
+            username: ensName,
+          });
+        }
+        if (!changeOccurred) {
+          return entity;
+        }
+        return {
+          ...entity,
+          uiName,
+        };
+      } else {
+        return entity;
+      }
+    })
+    .filter(Boolean);
 }
 
 function useENSNamesForEntityText(entityText: ?EntityText): ?EntityText {